The table below includes entries for popular substances already used for their energy, or being discussed for such use.

The second column shows specific energy, the energy content in kilojoules per unit of mass in kilograms, useful in understanding the energy needed to ship the fuel, which takes away from its net energy contribution.

The third column in the table lists energy density, the energy content per liter of volume, which is useful for understanding the space needed for storing the fuel.

The final two columns deal with the carbon footprint of the fuel. The fourth column contains the proportion of CO2 released when the fuel is converted for energy, with respect to its starting mass, and the fifth column lists the energy produced per kilogram of CO2 produced. As a guideline, a higher number in this column is better for the environment. But these numbers do not account for other green house gases released during burning, production, storage, or shipping. For example, methane may have hidden environmental costs that are not reflected in the table. [1]

^While all CO2 gas output ratios are calculated to within a less than 1% margin of error(assuming total oxidation of the carbon content of fuel), ratios preceded by a Tilde (~) indicate a margin of error of up to (but no greater than) 9%. Ratios listed do not include emissions from fuel plant cultivation/Mining, purification/refining and transportation. Fuel availability is typically 74–-84.3% NET from source Energy Balance.